Thermally switched reflective optical shutter

• US 8,072,672 B2
• Filed: 07/02/2010
• Issued: 12/06/2011
• Est. Priority Date: 07/11/2007
• Status: Active Grant

• Current Assignee: Ravenbrick, LLC
• Original Assignee: Ravenbrick, LLC
• Inventors: Powers, Richard M., McCarthy, Wil
• Primary Examiner(s): Spector, David N
• Application Number:
  US12/830,068
• Publication Number:
  US 20100271686A1
• Time in Patent Office: 522 Days
• Field of Search: 521/713, 257/14, 349/16, 349/163, 359/227, 359/265, 359/275, 359/288
• US Class Current: 359/288
• CPC Class Codes: E06B 2009/2464 featuring transparency control by applying voltage, e.g. LCD, electrochromic panels
• CPC Class Codes: E06B 9/24 Screens or other constructions affording protection against light, especially against sunshine; Similar screens for privacy or appearance; Slat blindsoperating, guiding or securing devices or arrangements for roll-type closures E06B9/56; free-hanging flexible screens A47H23/00
• CPC Class Codes: G02B 27/28 for polarising used in stereoscopes G02B30/25
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/0139 Polarisation scrambling devices; Depolarisers
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/132 Thermal activation of liquid crystals exhibiting a thermo-optic effect
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/133533 Colour selective polarisers G02F1/1347 takes precedence
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133538 with spatial distribution of the polarisation direction

Abstract

The thermally switched reflective optical shutter is a self-regulating “switchable mirror” device that reflects up to 100% of incident radiant energy above a threshold temperature, and reflects up to 50% of incident radiant energy below a threshold temperature. Control over the flow of radiant energy occurs independently of the thermal conductivity or insulating value of the device, and may or may not preserve the image and color properties of incoming visible light. The device can be used as a construction material to efficiently regulate the internal temperature and illumination of buildings, vehicles, and other structures without the need for an external power supply or operator signals. The device has unique aesthetic optical properties that are not found in traditional windows, skylights, stained glass, light fixtures, glass blocks, bricks, or walls. The device can be tailored to transmit sufficient visible light to see through in both the transparent and reflective states, while still providing significant control over the total energy transmission across the device.

Claims

1. A glass spandrel section for regulating the reflection of radiant energy comprising

a first reflective polarizer;

a second polarizer; and

a thermotropic depolarizer positioned between the first reflective polarizer and the second polarizer that adjusts polarization of incident light when below a threshold temperature, wherein

above the threshold temperature up to 100% of incident light is reflected by the device, and

below the threshold temperature up to 50% of incident light is reflected by the device.

2. The device of claim 1, wherein

at a first temperature a first percentage of the incident radiant energy is reflected from the device and a second percentage of the incident radiant energy is transmitted through the device;

and

at a second temperature a third percentage of the incident radiant energy is reflected from the device and a fourth percentage of the incident radiant energy is transmitted through the device.

3. The device of claim 1, wherein the second polarizer is an absorptive polarizer.

4. The device of claim 1, wherein either or both of the first reflective polarizer or the second polarizer are a diffuse reflective polarizer.

5. The device of claim 1, wherein either or both of the first reflective polarizer or the second polarizer are a polarity-rotating polarizer.

6. The device of claim 1, wherein the first reflective polarizer and the second polarizer each define transparent areas to allow transmission of unpolarized radiant energy through the device.

7. The device of claim 1 further comprising an electrotropic control system to supplement and actuate the thermotropic depolarizer at the threshold temperature.

8. The device of claim 1, wherein the second polarizer is a reflective polarizer.

9. The device of claim 8, wherein

the first reflective polarizer reflects up to 50% of the incident radiant energy and transmits a majority of non-reflected radiant energy;

and

the second polarizer reflects up to 100% of radiant energy transmitted by the first reflective polarizer when the thermotropic depolarizer is above the threshold temperature and transmits up to 100% of radiant energy transmitted by the first reflective polarizer when the thermotropic polarizer is below the threshold temperature.

10. The device of claim 1, wherein either or both of the first reflective polarizer or the second polarizer are a thermotropic reflective polarizer.

11. The device of claim 10, wherein

above a threshold temperature down to 0% of incident radiant energy is transmitted by the device, and

below the threshold temperature up to 100% of incident radiant energy is transmitted by the device.

12. The device of claim 1, wherein the thermotropic depolarizer comprises a liquid crystal.

13. The device of claim 12, wherein the liquid crystal further comprises an additive in a mixture with the liquid crystal to affect optical properties of the liquid crystal, a speed of transition between physical states of the liquid crystal, or both.

14. A window that regulates the reflection radiant energy comprising

one or more panes of glass:

a first thermotropic polarizer supported on one of the one or more panes of glass; and

a second thermotropic polarizer supported on one of the one or more panes of glass, wherein

above a threshold temperature down to 0% of incident radiant energy is transmitted by the window, and

below the threshold temperature up to 100% of the incident radiant energy is transmitted by the window.

15. The window of claim 14, wherein

at a first temperature a first percentage of the incident radiant energy is reflected from the device and a second percentage of the incident radiant energy is transmitted through the device;

and

at a second temperature a third percentage of the incident radiant energy is reflected from the device and a fourth percentage of the incident radiant energy is transmitted through the device.

16. The window of claim 14, wherein the first thermotropic polarizer and the second thermotropic polarizer are oriented with respect to each other such that a difference in alignment of polarity between the first thermotropic polarizer and the second thermotropic polarizer is less than 90 degrees.

17. The window of claim 14 further comprising a depolarizer positioned between the first thermotropic polarizer and the second thermotropic polarizer that at least partially adjusts a polarity of the radiant energy transmitted by the first thermotropic polarizer and reflected by the second thermotropic polarizer.

18. The window of claim 14, wherein either or both of the first thermotropic polarizer or the second thermotropic polarizer are reflective.

19. The window of claim 18, wherein the either or both of the first thermotropic polarizer or the second thermotropic polarizer are a wire grid polarizer.

20. The window of claim 19, wherein the wire grid polarizer further comprises a plurality of wire segments that change in shape or orientation in response to temperature.